Multi-material filament feeder/repurpose E1 stepper driver

jckray

@fma In occurs when loading the filament back in when right as the filament enters the nozzle. Some filaments, the breakaway in particular, have a slight bulge at the tip after unloading.

jckray

@red-sand-robot A supper rough BOM is now on our Thingiverse page along with updated files https://www.thingiverse.com/thing:2992637

gavatron3000

did the knife improve reliability? ive seen the prusa mmu2 struggle with the E3d breakaway also in videos

jckray

@gavatron3000 I have not tested the e3d breakaway since adding the cutting mechanism. I have had it up and running with the blade for a day and a half now. So far reliability is much better. I will let you know how the breakaway supports go once I have tested them.

fma

Where did you put the cutter? On the loader carriage, as Prusa did?

jckray

@fma Yes, it's on the carriage. I'll see if I can get some pictures.

jckray

@fma the cutter is using a standard Xacto knife blade. Here are some pics

fma

I'm thinking to add a cutter under the extruder. This way, cut tips stay in the hotend, and are pushed again by the new filament during the purge, so no need to evacuate them. Ideally, it would be nice to be able to cut the filament when it is still soften, above the melt chamber, but I don't think ti would be easy...

jckray

@fma No, that does not sound easy. We had to use the method we did because our tool head is pretty complex and already has a magnetic hotend cartridge system, so something like that would not fit on our tool head and would make that portion of the printer too complicated.

fma

BTW, I made some quick tests cutting filament with hot wire (easy to build, with a NiCr wire + led current driver). I didn't not spend much time: it cut very well, but leaves some small borders on the tip of the filament. I need to dig further this method.

BTW, I'm wondering if having the nozzle drilled at 1.7mm instead of 2mm could help to avoid bad tips?

jckray

@fma That sounds interesting, would love to hear more if you ever to any more testing.

Yes, I have had the same thought about the diameter of the nozzle, however, this would mean you would only be able to use expensive filament with a very good manufacturing tolerance.

fma

Well, I said 1.7mm, but yes, 1.8mm would be better. But not 2mm...

Red Sand Robot

@jckray

Excited to see the progress on it! I for one would be interested in hardware kit, though I might try to see if it would be possible for me to fabricate some of the non printed pieces in my university's metal shop.

Is everything running well on the firmware side of things?

jckray

The firmware is running fine. We are still ironing out a few minor issues.

jckray

@red-sand-robot Glad to hear you would be interested in a kit. We will need to see interest from more people before we would make an official kit. However, if we don't do a kit we can definitely help you out with the hard to find/custom parts if you need them.

Red Sand Robot

@jckray How much, roughly, did the NEMA 17 with the custom shaft? I have already begun printing the parts for your MMU system, so far so good!

0_1540419781136_20181024_152242.jpg

jckray

@red-sand-robot The MOQ was 10 units, It was several hundred dollars for the whole order. I'd be happy to sell you one, so you don't have to deal with all that. I'll get the motor listed in the parts section of our website, and post here when it is there.

jckray

@red-sand-robot The Nema 17 with 100mm shaft is available on our website now https://www.hydraresearch3d.com/parts/qmpid8sbp277kcd25a9wrngcqywaqr-j3j2n

fma

BTW, did you consider using PTFE tube with ID of 2.5mm, instead of 2mm? This should solve a lot of issue coming from bad tips.

I'm waiting for mine (seems to have been lost between UK and France )

jckray

@dc42

Okay, it's been a little while. I couldn't seem to get this to work properly. In particular, I could not figure out how to configure the E1 end stop for the dummy axis.

Also is there any chance that an extrude until filament sensor is triggered feature could be added?

I'm trying to have the filament sensor serve to purposes.

During unloading of the filament detect the end of the filament. During the ramming and unload from the nozzle I have noticed a little variance in the length. This is likely due to the filament "breaking" and leaving slightly different amounts of filament in the hot zone. If I can detect the end of the filament, I can the be sure that I have backed the filament out far enough to not interfere when the filament selector when it moves to the next filament, but not too far that it disengages with the drive gear.

I'm hoping I can make this work by disabling the filament runout external trigger at the beginning of my unload script so as not to get a false runout detected. Then I want to unload until the filament sensor is triggered so I know where the end of the filament is and then unload the last little bit to clear the filament from the filament selector.

Normal filament sensing. My idea here is to enable the filament runout external trigger and the end of each load script.

I know this may be a little confusing, hopeful I made myself clear.